1. Field of the Invention
This invention relates to chemically pumped lasers of both a continuous and pulsed type based on chemical reactions of the azide radical. The invention provides a means of generating chemicals that react to produce electronically excited molecules, means to combine the energy of these molecules and means to cause this energy to be emitted in a coherent beam of radiation.
2. Background Information
One chemically pumped electronic transition laser that has been demonstrated is the iodine laser. This laser consists of two parts: (a) a chemical generation of O.sub.2 (a.sup.1 .DELTA.) by reaction of Cl.sub.2 with H.sub.2 O.sub.2 ; and (b) transfer of the energy of O.sub.2 (a.sup.1 .DELTA.) to I. EQU O.sub.2 (a.sup.1 .DELTA.)+I(.sup.2 P.sub.3/2).fwdarw.O.sub.2 (X.sup.3 .SIGMA.)+I(.sub.2 P.sub.1/2) EQU with subsequent lasing EQU h.nu.+I(.sup.2 P.sub.1/2).fwdarw.2h.nu.+I(.sup.2 P.sub.3/2).
These processes occur in a laser cavity. This laser emits in the infrared at 1.35.mu..
Major practical problems exist in generating, transporting, and mixing O.sub.2 (a.sup.1 .DELTA.) with iodine atoms. These are largely because O.sub.2 (a.sup.1 .DELTA.) is generated by the reaction of a gas with a liquid at low temperature and pressure while iodine atoms must be formed and interact with O.sub.2 (a.sup.1 .DELTA.) at higher temperatures in a gas stream from which contaminants from the O.sub.2 (a.sup.1 .DELTA.) generator must be removed.
Aside from these practical difficulties, the long wavelength of this laser is unsuitable for some applications. In particular, if it is desired to focus the radiation from a chemical laser onto a target, the area of the optical elements scales as the wavelength, .lambda., squared, .lambda..sup.2. Smaller optical elements resulting from a smaller .lambda. make a system less expensive and lighter in weight as well as smaller.
The general concept of a short wavelength chemical laser is simply to generate, by chemical reactions, electronically-excited product molecules capable of sustaining laser action. In practice, most chemical reactions give ground electronic state products. Those that do not generally give products in their first excited metastable state. This state, aside from having a small stimulated emission cross section, is usually quite low in energy (.about.1 eV, 23 kcal/mole) and so unsuitable for visible lasing.
One way to generate more highly electronically excited molecules is to pool the energy of two less excited species. Indeed, this occurs in the "upconverter" laser EQU H+NF.sub.2 .fwdarw.HF+NF(a.sup.1 .DELTA.) EQU h.nu.+I(.sup.2 P.sub.3/2).fwdarw.I*(.sup.2 P.sub.1/2) EQU NF(a.sup.1 .DELTA.)+I*(.sup.2 P.sub.1/2).fwdarw.NF(b.sup.1 .SIGMA.)+I(.sup.2 P.sub.3/2)
Unfortunately, NF(b.sup.1 .SIGMA.) is also metastable and unsuitable for lasing. It has been suggested that its energy be extracted by collisional energy transfer to a lasing molecule, such as IF EQU NF(b.sup.1 .SIGMA.)+IF(X.sup.3 .SIGMA.).fwdarw.NF(X.sup.3 .SIGMA.)+IF(B.sup.1 .pi.).
Unfortunately, this energy transfer is very slow while the reaction between NF(b.sup.1 .SIGMA.) and IF(X) is very fast.
Other methods of utilizing the energy stored in NF(a.sup.1 .DELTA.) have been suggested. For example, reaction of NF(a.sup.1 .DELTA.) with Bi atoms has been shown to produce emission from BiF* which is approximately twice as energetic as the emission from NF(a.sup.1 .DELTA.). Such a laser has not been demonstrated.